Nanoindentation is a method to quantitatively measure the mechanical properties of a test sample, such as elastic modulus and hardness, for example, using a small force and a high resolution displacement sensor. Typically, a force employed in nanoindentation is less than 10 mN, with a typical displacement range being smaller than 10 μm, and with a noise level typically being better than 1 nm rms. In nanoindentation, a nanoindenter capable of determining the loading force and displacement is used. The force and displacement data are used to determine a sample's mechanical properties. For this sample property estimation, a nanoindenter has to be integrated with a characterized tip which has known geometry and known mechanical properties. A nanoindenter with two dimensional force and displacement sensing can be used as a nano-tribometer for tribological applications for measuring additional mechanical properties such as friction and wear.
One of the key components in nanoindentation instrumentation is a transducer which converts an electrical input into a mechanical force and a mechanical displacement into an electrical signal. A well designed nanoindenter transducer can improve many aspects of the nanoindenter performance such as increasing the range of forces, including increasing the maximum force, improving force resolution and system bandwidth, and reducing system noise.
One of the emerging nanoindentation applications is quantitative in-situ nanomechanical testing within a transmission electron microscopy (TEM). This testing method enables monitoring of the deformation of a sample in real time while measuring the quantitative mechanical data. To achieve such testing capabilities, a quantitative transducer capable of applying force and measuring displacement should be integrated with a TEM holder. The physical size of the transducer is limited by the size of the TEM holder, which depends on the pole gap of the TEM. For example, TEM holders manufactured by FEI have a maximum allowable outer diameter of 4 mm, and some TEMs having smaller holder diameters, require a small transducer in order to be compatible with FEI and Hitachi TEMs.
In view of the above, the physical size of the tribometer must be reduced. The importance of making smaller tribometers is evident from TEM market data which shows FEI and JEOL each have a 40% market share, with various others having the remaining 20%. Making a smaller tribometer will enable expansion of in-situ nano-tribology testing capabilities to FEI and some other TEMs. MEMS technology is one technology which enables miniaturization the nano-tribometer without detracting from performance requirements.
A 1-Dimensional (1-D) MEMS transducer has been developed, as described by U.S. patent application Ser. No. 12/497,834, filed on Jul. 6, 2009, which is assigned to the same assignee as the present disclosure, and which is incorporated by reference herein. However, such MEMS transducer provides actuation and sensing along a single axis (i.e. 1-dimensional), that being along an axis of indentation.